In Arizona’s low desert, the best Asian greens are the quick leafy types: baby bok choy, tatsoi, mizuna, komatsuna and the milder mustards, grown from fall through early spring. Amaranth and water spinach take the summer heat that wilts the rest. At higher elevations the same quick greens work in spring and early fall. Heat and speed decide the pick far more than frost does.
The short answer for Arizona
Phoenix is the usual reference point for the low desert, and its climate numbers explain the choice. NOAA lists the frost-free season there as 365 days. The thermometer hit 32°F in only 6 of 30 springs, and in a rare cold snap it happens between late December and mid January. The mean daily minimum of the coldest month is 45.3°F. Winter cold almost never stops a leafy green in the low desert. Summer heat does, so the question for each variety is how fast it finishes and how much heat it can take.
Which Asian greens suit the low desert?
Baby bok choy, tatsoi, mizuna and komatsuna are the dependable core. They produce edible leaves quickly, and you can cut them young. They are happiest when days are mild and nights are cool, which in the low desert means roughly the cooler half of the year. Red and green mustards (the Japanese types are milder) grow just as fast and take a little more cold. Gai lan and choy sum, the Chinese broccoli and flowering greens, do well in the same window, and their flower stalks are the part you eat, so bolting is less of a loss.
Summer needs a different set of plants. Amaranth, sold as Chinese spinach or yin choy, grows fast in hot weather and keeps making tender leaves. Water spinach (ong choy) also loves heat, though it wants constant moisture. Neither will taste like bok choy, but they fill the months when the cool-season greens are not an option.
| Type | Low desert (Phoenix area) | High country (Flagstaff area) |
|---|---|---|
| Baby bok choy, tatsoi, mizuna, komatsuna | Fall through early spring | Spring once hard freezes pass, and early fall |
| Mustards, gai lan, choy sum | Fall through early spring | Spring and early fall, with row cover |
| Napa cabbage | Difficult; needs a long cool stretch | Best chance in a cool fall |
| Amaranth, water spinach | Summer heat | Short and marginal; only in the warmest weeks |
Which Asian greens suit the high country?
Flagstaff and the high country freeze hard, and they follow a calendar closer to the northern states than to Phoenix. Bok choy, tatsoi, mizuna and mustards all do well there in spring and again in early fall. Heat-lovers like amaranth have little time to work with. For the month-by-month sowing windows, see When to Sow Asian Greens in Arizona. The broader overview is in Growing Asian Greens in Arizona.
What will not work here
The most common mistake in the low desert is sowing bok choy in spring because the calendar says the last frost has passed. A frost-date rule is meaningless in Phoenix, where most years never freeze. By the time the soil feels like spring in March or April, heat is already a few weeks away, and the plants bolt before they size up. Sowing by frost date works in Flagstaff. In the low desert it points you at the worst window.
Summer sowings of the cool-season greens fail too. Bok choy, tatsoi and mizuna sown into hot soil sprout poorly or run to seed almost at once. Napa cabbage is the toughest case. It needs a long stretch of cool weather to form a tight head, and low-desert falls often turn warm again before the head fills. Many gardeners there give up on napa and grow the loose-leaf types, which are forgiving.
A weekly watering habit does not hold up in a hot, dry climate either. Asian greens have shallow roots, and in warm spells the top few inches of desert soil can dry out in a day. A deep soak once a week leaves the plants stressed between waterings, and stressed greens turn bitter and tough. Mulch helps, and so does a drip line that keeps the root zone evenly moist. In warm weather that may mean watering most days.
Plan for sun as well as heat. Low-desert afternoon sun scorches thin leaves even in the cool season, so a spot with shade after midday, or a light shade cloth, protects them. In summer, shade is the difference between amaranth and water spinach that thrive and plants that crisp at the edges. Desert soil is often alkaline and low in organic matter, and many yards have a hard caliche layer under a thin topsoil. Raised beds filled with compost-rich mix sidestep both problems.
In the high country the failures run the other way. A warm week in April can tempt you into planting tender seedlings, and a late hard freeze then kills them. Slow, heading varieties may not finish before fall freezes return. In cold spots, quick baby greens beat anything that needs a long season.
What changes across Arizona
Arizona is not one garden. The USDA Plant Hardiness Zone Map (2023 edition, built on 1991-2020 normals) runs from 4b to 10b across the state. That covers a wide range of zones, from 4b to 10b. No single recommendation fits that spread, which is why the Phoenix numbers above are a reference for the low desert and not a statewide rule.
The zone system rests on a single measurement, the average annual extreme minimum temperature. It tells you how cold the worst night gets, which matters for perennials, and it says nothing about how hot July is. Two gardens in different zones might both bake in summer, and two in the same zone can differ because of elevation, cold air pooling in a valley, or a south-facing wall. Treat the zone as one clue.
If you garden in the north or at altitude, shift the whole schedule. Spring sowing waits until the soil has thawed and the hardest freezes have passed, and fall sowing goes in earlier, in late summer, so the crop is up before the cold. Low tunnels or row cover stretch both ends of the season. Choose fast varieties over heading types, and expect to harvest baby leaves.
Mid-elevation towns sit between the extremes. They may get real winter freezes but milder summers than Phoenix, so a longer spring and fall window for cool-season greens is likely. To see where your own garden falls, look up your location on the USDA Plant Hardiness Zone Map instead of guessing from the state average. Then compare it with what your neighbors actually grow.
Where to check this for your own county
The state-level answer here is a starting point. A county recommendation is better, because it reflects local elevation, soil and the dates that gardeners nearby have recorded. The place to go is University of Arizona Cooperative Extension, which has offices across the state, each with staff who know their county’s growing conditions.
Two things are worth looking for. First, the local planting calendar for vegetables, which tells you when to sow leafy greens in your part of the state. A calendar for a low-desert county will look very different from one for a county at 7,000 feet. Second, any variety trials. Extension offices and the Master Gardener programs attached to them sometimes grow cool-season greens side by side and note which bolt early, which handle heat, and which pests show up.
Ask your county office about local pests as well. Aphids and flea beetles go after Asian greens in different seasons in different parts of the state. Ask about irrigation water too. In some areas the water is salty enough to affect leaf quality, and a county agent can tell you what to do about it.
Checking this against your own garden
Your own observations outrank any date in any guide. Three are easy to make without any equipment.
- Soil warmth by feel. In the morning, push your hand a few inches into the bed. If the soil is cool, cool-season greens will sprout. If it feels warm at sunrise, the bed is already too hot for bok choy. Beds against a south wall or on bare ground warm up first.
- The first true leaves. Seedlings first show two rounded seed leaves, then the first true leaves with the shape of the mature plant. Fast, steady growth to that stage means the spot suits the crop. A seedling that stalls or yellows there is under heat, dry soil or too much sun.
- The first sign of bolting. Watch the center of tatsoi, mizuna and bok choy for a tight cluster of flower buds or a stem starting to stretch. The date that first appears is the end of the season in your yard, so write it down and sow earlier next year.
Keep notes for a year or two. A shady corner behind the house may stretch the harvest by weeks compared with an open bed, and only your own record shows it.
Common questions
Which Asian green handles Arizona heat best?
Amaranth and water spinach are the strongest in summer. Both keep producing leaves in hot weather, as long as the soil stays moist. Water spinach needs the most water of the two.
Can I grow napa cabbage in the low desert?
It is possible but difficult. Napa needs a long, cool stretch to form a full head, and low-desert falls can warm up too soon. Loose-leaf Asian greens are far more reliable there. In the high country, a cool fall gives napa its best chance.
Do I need frost protection in Phoenix?
Rarely. NOAA records show 32°F in only 6 of 30 springs at the Phoenix reference station, and a cold snap can come between late December and mid January. Keep a light cloth handy for those nights. At higher elevations, plan on row cover or low tunnels as standard equipment.
How often should I water Asian greens in Arizona?
Often enough that the top few inches of soil never dry out completely. Their roots are shallow, so a weekly deep soak is not enough in warm, dry weather. Mulch and drip irrigation cut the number of times you have to water, and in warm spells you may still water most days.